(57) The hydraulic brake adjuster (10) and piston assembly (30) include an exterior valve
(11) which is disposed separate from a piston (32). The exterior valve (11) includes
a differential area valve piston (12) receiving actuation fluid pressure and an outlet
(26) which communicates fluid pressure to the piston assembly (30). The piston assembly
(30) includes a piston bushing (40) received within the piston (32) to define substantially
therebetween a pair of longitudinal pressure chambers (50, 95), a recessed piston
(60) received within the piston bushing (40) to define therebetween an axial pressure
chamber (70), the axial pressure chamber (70) comunicating with one (50) of the pair
of longitudinal pressure chambers (50, 95), and the one longitudinal pressure chamber
(50) receiving actuation fluid pressure. A piston valve (90) is located within an
interior opening (97) in the piston (60), the interior opening (97) communicating
with the axial pressure chamber (70). The piston valve (90) extends through front
(74) and rear (68) wall openings of the piston (60), and is biased by a spring (94)
toward the rear wall (66). The rear wall (66) of the piston (60) and the bushing (40)
define a portion of the other longitudinal pressure chamber (95) which communicates
with the outlet (26) of the exterior valve (11).
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